This invention relates to a toner for developing electrostatic images usable in the fields of electrophotography, electrostatic recording, and the like.
In the electrophotography and electrostatic recording, a printed image can be produced, for example, by steps of forming an electrostatic image on a photoconductive layer by a various kinds of means, developing the electrostatic image with toner particles, transferring the toner which formed the image to a transferring material such as paper, Mylar film, etc., and fixing with heated rolls, pressure rolls, heated pressure rolls, or flash light from a xenon lamp.
Copied products are sometimes stored in a file containing sheets of non-rigid polyvinyl chloride in order to prevent stain and damage and to use for a long period of time.
As toners for developing electrostatic images usable in the electrophotography and electrostatic recording, there have been known toners using vinyl resins such as a toner using a polystyrene resin (Japanese Patent Appln Kokoku (Post-Exam Publn) No. 16118/69), a toner using a styrene-butyl methacrylate copolymer resin (Japanese Patent Appln Kokoku (Post-Exam Publn) No. 1143/81), etc., a toner using a bisphenol type epoxy resin obtained by reacting a bisphenol with epichlorohydrin (Japanese Patent Appln Kokai (Laid-Open) No. 96354/82), a toner using a polyester resin obtained by reacting a glycol having a bisphenol skelton with a polybasic acid (U.S. Pat. No. 3,681,106) and the like. Since the vinyl resins can be controlled in wide range regarding physical properties such as molecular weight, glass transition point, molten viscosity, etc., and are very advantageous for designing toners, almost toners are obtained by using these vinyl resins. But the toners hereto known using vinyl resins have a fatal defect in that when copied products obtained by using such toners are stored in contact with sheets of non-rigid polyvinyl chloride, the printed letters and images are adhered to the sheets to produce defects of printed letters and images and to make it impossible to read the letters and images.